Yes, impaction and constipation should best be avoided before labor. Labor is long enough without the added tightening of intestinal muscles. You want to be as relaxed as possible. Magnesium is great for relaxing smooth muscle and reducing pain (period cramps and more). Many Nutrients, vitamins, minerals can be absorbed easily from juicing raw fruits and vegetables.
Fruits should be juiced separately from vegetables. Only apples may be added to veggies.
Please visit the Raw food Forum (this means recipes with raw fruits, veggies, nuts, nutbutters, seeds, carob, cocnuts, wild herbs--no meat nor dairy). You do not have to choose an all liquid diet to avoid impaction. Raw foods are rich in enzymes and help keep the bowel moving.
I know a woman who ate raw for two pregnancies and she was in labor for 45 minutes each time. When she ate cooked vegetarian foods, she was in labor for 10 hours. Besides that testimony, it makes sense that the nutrients and enzymes from the fresh , living foods will give more life to the cells and organs of the body. In this way, we can function at our optimum level.
There are many books and websites posted on Raw forum about juicing and Raw recipes and also health facts.